Hydroponics Root Rot: What is It, How To Treat It, How to Prevent It

Root rot is one of the most common plant conditions that you will encounter as a hydroponics grower.

It affects both indoor and outdoor setups, but it is more common in hydroponically grown plants that are kept indoors and have poor circulation.

Water circulation dictates the level of oxygenation and aeration that a plant receives over time and the less oxygen there is for the root mats to absorb, the higher the chances of a plant succumbing to root rot.

What happens to a plant when root rot occurs?

In a conventional gardening setup, root rot occurs when the gardener or grower overwaters his plants.

The soil is inundated with water, and due to the volume of the water and the type of soil used to grow the plant, the water doesn’t percolate through the soil quickly enough. Moisture stagnates around the roots of the plants, causing root rot.

Essentially, root rot occurs when the roots of the plants become strangled with so much water and it cannot breathe.

Do the root mats of plants actually breathe? Yes! Contrary to common belief, the roots of plants still require dissolved oxygen and oxygen from the environment to thrive.

In fact, aeroponics has proven time and time again that heightened exposure to atmospheric oxygen increases not just the size of the crop but also drastically increases the rate at which plants grow.

In a hydroponics setup, the usual cause of root rot is poor circulation.

When there isn’t much movement or when the roots of plants are submerged for long periods of time with very little access to atmospheric oxygen, root rot is bound to happen.

The culprit in cases of root rot is actually a type of water-borne fungi from the genus Phytophthora.

Molds prefer low-oxygen and highly moist environments and therefore, they are commonly found in live plant material where there is shortage of dissolved or atmospheric oxygen.

How can you treat root rot?

Know what they look like

The first thing you have to know about root rot is it actually looks quite disgusting up close.

Roots that are infest with the water-borne mold will look extremely slimy, almost bulbous in some parts and will be brown. You will also detect a faint (or not so faint), earthy smell emanating from an infected roots.

Take note that discoloration is not the number one symptom of root rot.

Often, roots that are submerged in any kind of nutrient solution will have some staining.

Nutrient staining is quite normal and if you smell the root mass, you won’t smell any earthy about it – precisely because there is no ‘earth’ in a hydroponic system.

You might smell the nutrient solution or the natural smell of the plant (herby smell) but not earthy.

Many hydroponics growers throw their hands up when they see root rot. They believe that it’s the end of that batch of plants and nothing could be done.

And in some cases, this is true: it would be easier to simply start over than to try to treat the root mats.

However, if the infection has just begun and you think that your plants are salvageable, then by all means, try to treat the water-borne fungi.

The basic treatment for root rot is the application of beneficial bacteria to the nutrient solution.

Add beneficial bacteria to the nutrient solution

Beneficial bacteria help fight the proliferation of fungi and serve as root protectors, too.

These beneficial bacterial cultures are marketed as root protectors, though there are many brands and you should definitely check out the reviews for each one before purchasing.

Using beneficial bacteria is extremely popular for the indoor hydroponics crowd, because root rot is so common and if you apply the beneficial bacteria to the system before planting, you can establish a solid protective system for your plants easily.

Use air pumps to add bubbles

The second type of treatment for root rot if it’s not so pervasive yet is adding more bubbles to your growing trays/containers. Why bubbles?

Bubbles help draw oxygen from the atmosphere and a water pump can directly help increase the amount of dissolved oxygen in your growing trays/rafts/containers.

Just as air pumps help fish survive in the constrained space of an aquarium, so can this device help tone down cases of root rot in your hydroponics setup.

To help save you time, money and effort, we suggest piping the air throughout your grow beds so that bubbles are well-distributed throughout your grow beds.

A single pipe running through your grow beds with holes at specific intervals (aimed at the roots of the plants) can directly increase the dissolved oxygen at sites that require the most dissolved oxygen (i.e. the root mats).

Keep those roots in the dark

This may come as a surprise to many of you, but the roots of plants do not like light. And light can also trigger the growth of other organisms that we do not want or need in the nutrient reservoir.

It’s important that you are able to keep the root areas of your plants in pitch darkness.

Either add some cover if there are some cracks where light can pass through, or check the gaps and add some dark filling material that can stay in place permanently.

You won’t have any problems with your pots since they will stay the same shape and size throughout the growing season.

And if your growing cups or net pots are of a standard size, you can replace them easily later on to plant a new batch of crops.

How can you prevent root rot?

Prevention is really, 100% better than trying to cure root rot.

When there’s root rot already, that means you’ve failed to take some essential precautions in keeping your hydroponics setup clean and efficient.

But don’t fret: you can prevent root rot from happening again. Here are the steps.

Keep your greenhouse as cool as possible

If you have an outdoor hydroponics setup in a greenhouse, you definitely have to control the ambient temperature inside the greenhouse.

Apart from protecting the plants from undue withering, a cooler clime inside your outdoor setup will help cool the nutrient solution down, making dissolved oxygen more available to the roots of your plants.

Unfortunately, it has been proven that warmer water tends to let go of oxygen more quickly.

The same principle applies if you have an indoor setup at home. No matter how small your indoor setup may be, the plants, water and lighting will generate some heat.

Trapped heat, even in small increments over time, can warm the water, making your plants’ roots more susceptible to root rot.

Adding exhaust fans to an indoor setup is definitely a good idea and checking the regular temperature is a must.

Your target temperature is between 75 to 85 degrees Fahrenheit. This is only an ideal range.

You can still grow lots of plants beyond 85 degrees; however, the risk of encountering root rot increases, too.

Keep those roots pristine

In addition to not disturbing the roots of your plants, there’s something you need to do at flowering stage or early stage of development to ensure that you will get better results: don’t change the water in the reservoir.

The water in your reservoir is essentially an ecosystem in itself, with both beneficial and harmful bacteria.

Every week, this ecosystem approaches balance more and more, and this is what we really want to happen – we want those young roots to be able to grow as the ecosystem balances itself.

Eventually, a protective and beneficial biofilm layer will form over the root mat of your young plants, protecting the root mats from damage and molds.

So the big lesson here is don’t change the water for young plants – simply top up with additional nutrient solution, but keep the old water.

That old water is hydroponic gold because of its beneficial bacterial population.

If you start off strong, you’re going to have more resistant plants in the future that can fend for themselves even if the conditions in your hydroponics setup are less than ideal.

Sterilize and clean

Any and all equipment should be cleaned and sterilized regularly.

The reason for this is whenever you dip into that nutrient solution, you’re actually dipping into a broth teeming with bacteria and other microscopic denizen.

You don’t want those denizens to proliferate in other parts of your system, but your equipment will eventually ‘touch’ all parts of your system, too.

So we have no choice, we have to keep your tools and gear clean.

What about outdoor setups? Those boots and shoes are teeming with microorganisms, too!

It would be best to put a stepping pan right in front of the door to the your greenhouse so you can disinfect your shoes.

Household bleach can be mixed with water so there’s a ‘bath’ that can kill most germs when people step into the solution.